Mainformontaskbar delphi 7 ошибка

• Up to Parent: TApplication

property MainFormOnTaskBar: Boolean read FMainFormOnTaskBar write SetMainFormOnTaskBar;

__property bool MainFormOnTaskBar = {read=FMainFormOnTaskBar, write=SetMainFormOnTaskBar, nodefault};

Properties

Description

Controls how Windows taskbar buttons are handled in a VCL application.

If the MainFormOnTaskBar is True, a taskbar button represents the application’s main form and displays its caption. If False, a taskbar button represents the application’s (hidden) main window and bears the application’s Title.

MainFormOnTaskBar must be True to use Windows Vista or Windows 7 Aero effects, including live taskbar thumbnails, Dynamic Windows, Windows Flip, and Windows Flip 3D.

If a change to the default behavior is required, MainFormOnTaskBar should be set in the project source file after Application.Initialize and before the main form creation. The MainFormOnTaskBar setting is intended to persist for the life of the application; later run-time changes of this property could result in unexpected behavior.

MainFormOnTaskBar defaults to True for applications created in Delphi 2007 and later products, and to False for earlier products.

The MainFormOnTaskBar property can be applied to older applications. Note that it affects the Z-order of your MainForm in case your application depends on this.

To update existing VCL applications, add the following line to the project source file (example includes the application initialization line, which must precede the line that sets MainFormOnTaskBar):

Delphi:

Application.Initialize;
...
Application.MainFormOnTaskbar := True;

C++:

Application->Initialize();
Application->MainFormOnTaskBar = true;

Note that the line is automatically added to new projects.

For further information, see http://www.microsoft.com/windows/products/windowsvista/features/experiences/aero.mspx.

See Also

• TApplication

Code Examples

• TAppCreateForm (Delphi)
• TAppCreateForm (C++)

I built the code below using Delphi XE2. It creates Form1, and Form1 immediately creates an instance of Form2. When I press the button on Form2 a second Form2 is created.

Now if I hover the mouse over the button on this second, topmost, Form2 and wait for the tooltip to appear, the moment the tooltip appears, the first Form2 comes to the front, stealing focus.

The problem occurs only if Application.MainFormOnTaskbar is True. It also relies on the first Form2 being created from Form1’s FormCreate method. If I use PostMessage() to delay the creation of the first Form2 until the application has finished initialising, the problem goes away.

I’d like to understand why this is happening. I have already learned that Delphi’s Application object handles a lot of things including hint display, and I know that Delphi can recreate a window’s handle during initialisation, but I haven’t been able to follow this through to explain fully the behaviour described above (or indeed whether the above two facts are even relevant).

Project1.dpr

program Project1;

uses
  Vcl.Forms,
  Unit1 in 'Unit1.pas' {Form1},
  Unit2 in 'Unit2.pas' {Form2};

{$R *.res}

begin
  Application.Initialize;
  Application.MainFormOnTaskbar := True; // False makes problem go away
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

Unit1.pas

unit Unit1;
interface
uses
  Vcl.Forms, Unit2;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  public
    procedure CreateForm2;
  end;

var
  Form1: TForm1;

implementation
{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  CreateForm2;
end;

procedure TForm1.CreateForm2;
var
  frm : TForm2;
begin
  frm := TForm2.Create(Application); // (Could pass Self - makes no difference)
  frm.Show;
end;

end.

Unit2.pas

unit Unit2;
interface
uses
  Vcl.Forms, System.Classes, Vcl.Controls, Vcl.StdCtrls, WinApi.Windows;

type
  TForm2 = class(TForm)
    Button1: TButton; // This button has a hint
    procedure Button1Click(Sender: TObject);
  end;

var
  Form2: TForm2;

implementation
uses
  System.SysUtils, Unit1;

{$R *.dfm}

procedure TForm2.Button1Click(Sender: TObject);
begin
  Form1.CreateForm2;
end;

end.

I built the code below using Delphi XE2. It creates Form1, and Form1 immediately creates an instance of Form2. When I press the button on Form2 a second Form2 is created.

Now if I hover the mouse over the button on this second, topmost, Form2 and wait for the tooltip to appear, the moment the tooltip appears, the first Form2 comes to the front, stealing focus.

The problem occurs only if Application.MainFormOnTaskbar is True. It also relies on the first Form2 being created from Form1’s FormCreate method. If I use PostMessage() to delay the creation of the first Form2 until the application has finished initialising, the problem goes away.

I’d like to understand why this is happening. I have already learned that Delphi’s Application object handles a lot of things including hint display, and I know that Delphi can recreate a window’s handle during initialisation, but I haven’t been able to follow this through to explain fully the behaviour described above (or indeed whether the above two facts are even relevant).

Project1.dpr

program Project1;

uses
  Vcl.Forms,
  Unit1 in 'Unit1.pas' {Form1},
  Unit2 in 'Unit2.pas' {Form2};

{$R *.res}

begin
  Application.Initialize;
  Application.MainFormOnTaskbar := True; // False makes problem go away
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

Unit1.pas

unit Unit1;
interface
uses
  Vcl.Forms, Unit2;

type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  public
    procedure CreateForm2;
  end;

var
  Form1: TForm1;

implementation
{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
  CreateForm2;
end;

procedure TForm1.CreateForm2;
var
  frm : TForm2;
begin
  frm := TForm2.Create(Application); // (Could pass Self - makes no difference)
  frm.Show;
end;

end.

Unit2.pas

unit Unit2;
interface
uses
  Vcl.Forms, System.Classes, Vcl.Controls, Vcl.StdCtrls, WinApi.Windows;

type
  TForm2 = class(TForm)
    Button1: TButton; // This button has a hint
    procedure Button1Click(Sender: TObject);
  end;

var
  Form2: TForm2;

implementation
uses
  System.SysUtils, Unit1;

{$R *.dfm}

procedure TForm2.Button1Click(Sender: TObject);
begin
  Form1.CreateForm2;
end;

end.

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